I want when hit this button the client browse for some file in the computer the send it
It is not matter to send it to single user or all user
just want the file to be received correctle
Sorry for length
Sorry for bad english

Now, call the ChatMessage constructor with the bytes of your file and send that message over the wire.
At the other end the Client/Server who already switch on the type will have to add the case SENDING_FILE: in the switch()